Abstract

Crystallite-size-dependent variations in the Raman spectrum of rutile have been characterized and compared with those of the well-investigated rutile . For an average crystallite size below , the Raman spectrum of rutile nanocrystals displays an additional low-frequency, possibly surface vibrational, mode at . The disorder-activated, high-frequency surface modes seen in the Raman spectrum of rutile nanocrystals are absent. The and vibrational modes of rutile show systematic redshifts, broadening, and intensity reductions with decreasing crystallite size, which are consistent with phonon confinement behavior. A phonon confinement model provides reasonable crystallite size quantification, as in the case of rutile and .